1. Field of the Invention
The present invention generally relates to automobile wheels that are equipped with a decorative overlay. More specifically, this invention relates to an apparatus and a method for securing an overlay to an automobile wheel in a manner that promotes the integrity of the overlay-to-wheel bond using selective amounts of adhesive, the positional accuracy of the overlay on the wheel, and the manufacturability and consumer-perceived quality of the combined wheel and overlay assembly.
2. Description of the Prior Art
Decorative overlays are widely used to enhance the aesthetic appearance of automotive wheels. Overlays are not only employed to improve the appearance of unadorned standard steel wheels, but are also used with cast aluminum wheels, which are known to be expensive and difficult to plate with chromium. Numerous structural approaches for combining overlays with other steel or cast wheels have been suggested by the prior art, as well as methods by which overlays can be secured to a wheel. Many overlays are mechanically attached, for example, German Patent 2,813,412 mechanically attaches the overlay with cavities or undercuts in the face of the wheel. Further, Germany Patent 2,848,790 also teaches mechanical attachment of the wheel cover to the wheel through the use of clamps so that the cover can be removed for the purpose of cleaning. Others are adhered to the outboard surface of the wheel, as illustrated by U.S. Pat. No. 3,915,502 to Connell, which teaches an annular-shaped wheel cover that is permanently attached with double-sided adhesive tape to the wheel. The adhesive tape is positioned midway between the rim and the center hub area of the wheel, while the remainder of the wheel cover is spaced apart from the outboard surface of the wheel.
Connell presumably positions the adhesive tape at radially outward portions of the wheel in order to avoid the deleterious effects of heat generated by the tire, wheel and brake. While some pressure-sensitive adhesive tapes which can be effectively used in temperatures up to 500.degree. F. (260.degree. C.) are known and available, the cost of such adhesive tapes is generally prohibitive for use in mass production applications such as securing an overlay to a wheel. Consequently, such applications are generally limited to the use of less expensive adhesive tapes that have relatively low maximum operating temperatures, necessitating that their placement be restricted to the radially outward surfaces of the wheel. Unfortunately, doing so severely limits the adhesive tape's ability to reliably adhere the overlay to the wheel.
Another example of using an adhesive to bond an overlay to a wheel is taught by U.S. Pat. No. 3,669,501 to Derleth, which discloses an annular-shaped overlay composed of a thin plastic cover formed from acrylonitrile-butadiene-styrene (ABS) mounted to a wheel spider. The overlay is configured to have variations in contours in a direction transverse to the axis of the wheel which exceed the variations in the rim and/or disc contour of the wheel, which variations would be extremely difficult and expensive, if not impossible, to stamp or draw in the disc of the wheel. During assembly, an adhesive foamable polyurethane is coated on the wheel, and the cover is then quickly clamped to the wheel before the polyurethane begins to foam. As such, the void between the wheel and cover is filled with the polyurethane foam, and any excess polyurethane foam formed around the bolt holes or at the periphery of the assembly, that is, between the cover and the wheel, serves to permanently adhere the cover to the wheel.
Derleth teaches that the polyurethane foam adhesive provides a low-density, semi-resilient reinforcement for the thin gauge plastic cover while also providing sound insulation for tire and wind noise. However, it is understood by those skilled in the art that another reason for spacing the overlay's cover from the wheel surface is to avoid the deleterious effects of heat generated by the wheel and brake, which would otherwise distort the plastic cover and delaminate any surface treatment, i.e. paint, plating, etc., applied thereto. Further, the polyurethane foam adhesive completely breaks down at high temperatures experienced under certain actual road conditions. This is particularly true in the immediate region of the wheel hub where temperatures tend to be much higher than in the remainder of the wheel.
While the polyurethane foam adhesive taught by Derleth has an insulating effect, the thermal barrier provided by the foam adhesive is inferior to air. However, those skilled in the art will also appreciate that completely filling the cavity with the foam adhesive is advantageous in that doing so serves to acoustically damp any sound produced when the overlay is struck. Finally, the manner in which the foam adhesive is formed in situ on the wheel does not readily permit limiting the degree to which the foam adhesive fills the cavity.
An additional characteristic of the assembly method taught by Derleth is that the wheel must be available to the overlay manufacturer and handled during the assembly of the overlay to the wheel, rendering a manufacturing process which is somewhat complicated, awkward, and reliant upon the continuous availability of wheels, a condition which may be impractical for just-in-time manufacturing programs. Furthermore, timing of the processing steps used in the manufacture of Derleth's overlay is circumstantial in order to ensure that the cover is properly positioned, i.e. centered, over the wheel before the polyurethane begins to foam. Contrary to the method taught by Derleth, U.S. patent application Ser. Nos. 07/904,180 to Chase and 08/312,144 to Chase, both of which are assigned to the assignee of this invention, teach metal plated overlays that are formed independently and separately from the wheels to which they are to be attached. In particular, each of these overlays is formed of a metal-plated plastic panel that is permanently adhered directly to the surface of the wheel, preferably with a layer of a high temperature adhesive such as a silicone or polyurethane. Notably, the disclosed metal plating process enables the overlay to extend and cover high temperature regions of the wheel that prior art overlays are incapable of withstanding.
A further example of bonding an overlay to a wheel is taught by Beam in U.S. Pat. No. 5,368,370. Beam teaches an ornamental applique formed on a uniform thickness of stainless steel sheet stock which requires attachment to the wheel by the use of a full surface curable adhesive uniformly deposited between the stainless steel cover and a mechanical locking arrangement consisting of an undercut in the rim of the wheel into which the cover nests and a hole in the wheel aligned with a hole in the applique wherein a lug stud is permanently attached to create a mechanical lock which according to Beam's teachings compresses the full surface uniform layer of curable adhesive to hold the applique in place until the adhesive cures.
Beam's teachings present several problems. The mating of the stainless steel and the steel wheel at the rim area results in a galvanic action occurring which visibly is unacceptable in the marketplace. Further, at the hub portion of the wheel, the high temperatures experienced under certain driving or testing conditions may detrimentally affect the full surface uniform layer of curable adhesive while the cost of using a full surface curable adhesive is prohibitively expensive and wasteful since there is no need for a full surface uniform layer of adhesive to hold the overlay to the wheel. Further, a full surface uniform layer of curable adhesive also detrimentally affects the balancing considerations of the wheel and overlay assembly.
While such overlays have distinct advantages over previous overlays and assembly methods, further improvements are continuously sought. For example, a complication in the assembly procedure entailed with a separately formed overlay is that the position of the overlay with respect to the wheel rim must be accurately maintained while the adhesive cures, which can require several hours under optimal manufacturing conditions. Further desirable advancements include improving the overall manufacturability, performance, and consumer-perceived quality of the overlay and wheel assembly. However, such improvements are generally desirable only to the extent that any adverse effects on the weight, cost and balance of the resulting wheel assembly are avoided or minimized.
Accordingly, what is needed is an economical overlay apparatus and method for assembling such overlay to an automotive steel or alloy wheel, in which the method promotes the ability to accurately position and reliably permanently secure the overlay on the wheel by the use of selective application of an adhesive so as to improve the manufacturability of the wheel, reduce cost of manufacturing and not detrimentally affect wheel balance, performance and consumer-perceived quality of the wheel assembly.